The first and most important thing I tell them is to consider how much time it will take to train for their race. Many times someone who has a goal of running a 5K feels they do not have the time, with family, work, etc, to train. Their reference many times is a friend who races marathons (not 5K's) all the time and how much time they train. Or they hear how much a college athlete trains and tells themselves there is no way they can dedicate that much time to training. If your goal is to complete your first 5K, you don't have to commit the same amount of time.
If your goal is to do an Ironman, that will take a much larger time commitment and will take a lot of time away from your family and friends. You will have to evaluate if you are willing to commit this time. I encourage everyone to live an active life, but not at the expense of your happiness or your families.
To fit your training into your everyday life does not mean that you have to separate them. Encourage your significant other or friends to workout with you or do the same race. It will give you an opportunity to spend time with them. If you have children, get a running stroller. If they are older, have them go for a bike ride while you jog. You could do a 30 minute run while they bike at a pace you can chat with them (you can even do this with your significant other if they are willing to bike while you run). It will be a good pace for you to build some miles and spend time with your children. At the same time they get some exercise in as well. Get up early on a Saturday or a Sunday, get a workout in and then come home and make pancakes (or whatever your favorite breakfast is) for you and your kids. You will enjoy the breakfast and time with your family.
It is possible to fit training into your everyday life. Evaluate your goals and your time, but be honest with yourself. For the amount of time you can devote to training each week should not be any more then what you can do for 48-50 of the 52 weeks out of the year without having to make major sacrifices or changes to your life. When you train, to get the time in, be creative. Maybe there is a way you can train and spend time with your friends and family.